Agile does not dictate nor specify how to track and manage a budget in your Agile projects, but you can apply Agile principles and practices to the way you manage your budget by:
- Keeping it simple
- Making it succinct and valuable
- Focusing on an MVP = Minimum Viable Product
- Iterating and improving
In Project Management you would normally track expenses and resourcing costs on a monthly basis and in Agile that doesn’t need to change, you just need to match your Sprints to your budget timeline to reflect the expenses and resourcing costs of your Sprints in your monthly budget. Alternatively you could develop a Budget per Sprint if you prefer and if that would work best for you and your team.
Agile PMs generally use either a simple excel file to track their expenses and resourcing costs or they add addons to Trello or Jira such as these ones: Jira addon; Trello addon. You can find a simple Budgeting template in this Project Management course.